设 X = AFB, Y = CFE, Z = BFC = AFE。
X + Z = 72, Y + Z = 24,
Z/Y = BF/FE = X/Z
由此,有,
3 = (Z + X)/(Y + Z) = Z/Y.
Z = 24*(3/4) = 18.
阴影面积 = 2Z = 36.
设 X = AFB, Y = CFE, Z = BFC = AFE。
X + Z = 72, Y + Z = 24,
Z/Y = BF/FE = X/Z
由此,有,
3 = (Z + X)/(Y + Z) = Z/Y.
Z = 24*(3/4) = 18.
阴影面积 = 2Z = 36.